JP2014020463A - Radial foil bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial foil bearing that can have an excellent performance associated with load capability and dynamic characteristics of a bearing by reducing strain generated in a top foil, and is further improved in an attenuation effect.SOLUTION: There is provided a radial foil bearing 3 which supports a rotary shaft 1. The radial foil bearing includes a top foil 9, an intermediate foil 10, a back foil 11, and a bearing housing 12 which houses them. On both side faces of the bearing housing 12, engagement recessed parts 35 extending from inner peripheral edges to outer peripheral edges of the bearing housing 12 are formed opposite each other, and a plurality of pairs of those engagement recessed parts 35 are formed in a peripheral direction of the bearing housing 12. The intermediate foil 10 has a plurality of intermediate foil pieces 10a arranged along the peripheral direction of the bearing housing 12. The intermediate foil piece 10a has engagement projection pieces 10b which engage the engagement recessed parts 35 respectively.

Description

  The present invention relates to a radial foil bearing.

  Conventionally, as a bearing for a high-speed rotating body, a radial bearing used by being extrapolated to a rotating shaft is known. As such a radial bearing, a thin plate-like top foil that forms a bearing surface, a back foil that elastically supports the top foil, a cylindrical bearing housing that houses the top foil and the back foil, Radial foil bearings with are well known. As a back foil of the radial foil bearing, a bump foil obtained by forming a thin plate into a corrugated plate is mainly used.

  In some foil bearings, an intermediate foil is inserted between the top foil and the back foil for the purpose of improving the damping effect due to friction between the foils and reinforcing the rigidity of the top foil ( For example, see Patent Document 1).

In such a radial foil bearing, in order to prevent the top foil and the bump foil from falling off from the bearing housing, one end portion (stop end portion) of the radial foil bearing is usually directly attached to the bearing housing by spot welding or a spacer is attached. It is indirectly fixed through. Also, the intermediate foil is usually arranged so as to make one round of the bearing housing like the top foil and the bump foil, and one end thereof is fixed to the bearing housing by welding.
Also, in order to perform mechanical fixation instead of welding, the top foil and back foil (bump foil) end portions are bent by bending, and the bent portions are engaged with engagement grooves formed in the bearing housing. Are also known (see, for example, Patent Documents 2 to 4).

US Pat. No. 5,902,049 JP 2011-033176 A JP 2011-017385 A JP 2002-061645 A

  However, when the back foil (bump foil) is fixed to the bearing housing by welding, the back foil and the bearing housing are deformed by heat input, and the top foil is distorted due to this influence. Similarly, even if the intermediate foil is fixed by welding, the top foil is distorted. That is, when distortion occurs in the intermediate foil by welding, the distortion of the intermediate foil is also reflected in the top fill disposed thereon, and distortion occurs. Also, when the top foil and the intermediate foil are overlapped and welded together, the distortion of the intermediate foil that is the base is also reflected in the top foil, and the amount of distortion of the top foil becomes large.

  Moreover, since the top foil and the back foil are also bent in Patent Documents 2 to 4, the top foil is distorted. In other words, the top foil and the back foil are each distorted by bending. However, since the back foil supports the top foil, the back foil distortion affects the top foil, and the top foil distortion becomes larger. End up.

  However, the fluid lubrication film of the foil bearing formed between the rotating shaft and the top foil by the rotation of the rotating shaft is very thin at around 10 μm, so if any distortion occurs in the top foil, the load capacity of the bearing And dynamic characteristics (rigidity and damping) may be affected, and performance as designed may not be obtained.

  Further, conventionally, when an intermediate foil is used, the intermediate foil is arranged so as to make one round of the bearing housing. However, when it is arranged so as to be wound once, the number of constrained portions due to friction between the intermediate foil and the back foil or between the intermediate foil and the top foil increases, and slipping hardly occurs. However, when slipping does not easily occur in this way, it is considered that the damping effect due to friction caused by slipping is reduced.

  The present invention has been made in view of the above circumstances, and the distortion generated in the top foil is sufficiently reduced so that good performance as designed can be obtained as to the load capacity and dynamic characteristics (stiffness and damping) of the bearing. Furthermore, it aims at providing the radial foil bearing which the damping effect improved by the friction between foils.

The radial foil bearing of the present invention is a radial foil bearing that is extrapolated to a rotating shaft and supports the rotating shaft,
A cylindrical top foil disposed to face the rotating shaft, an intermediate foil disposed radially outward of the top foil, a back foil disposed radially outward of the intermediate foil, and the top foil A cylindrical bearing housing that accommodates the intermediate foil and the back foil in an inserted state,
Engaging recesses extending from the inner peripheral edge to the outer peripheral edge of the bearing housing are formed opposite to each other on both side surfaces of the bearing housing, and the pair of engaging recesses are arranged in the circumferential direction of the bearing housing. Is formed in multiple,
The intermediate foil is configured to have a plurality of intermediate foil pieces arranged along the circumferential direction of the bearing housing,
The intermediate foil pieces are formed with engaging protrusions that engage with the engaging recesses, respectively.

In this radial foil bearing, the intermediate foil is constituted by a plurality of intermediate foil pieces arranged along the circumferential direction of the bearing housing, so that the single intermediate foil wraps around the bearing housing once. Compared with the case where it arranges, the restraint location by the friction between foil reduces, and it becomes easy to occur slip between each intermediate foil piece, a back foil, and a top foil. Therefore, the damping effect due to friction caused by sliding increases.
In addition, since the engagement protrusions formed on the intermediate foil pieces are engaged with the engagement recesses formed on both side surfaces of the bearing housing, spot welding or large bending processing is performed on each intermediate foil piece. The intermediate foil made of the intermediate foil piece can be accommodated and fixed in the bearing housing. Therefore, the top foil is prevented from being distorted by spot welding of the intermediate foil or the distortion of the intermediate foil, and the distortion of the top foil is sufficiently reduced. Further, since the intermediate foil is not required to be welded, it is possible to eliminate the assembly failure and the assembly variation due to the welding failure. Further, when the intermediate foil piece is damaged or worn out, it is only necessary to replace the damaged or worn part (intermediate foil piece) without replacing the entire intermediate foil.

Further, in the radial foil bearing, the back foil includes a plurality of back foil pieces arranged along a circumferential direction of the bearing housing, and the engaging projection piece of the intermediate foil piece includes: It is preferable to engage with the engaging recess through a gap formed between a plurality of back foil pieces.
Since the back foil elastically supports the top foil via the intermediate foil, when receiving a load from the top foil, the back foil is deformed in the circumferential direction to allow the top foil to bend and support it. . However, when the back foil is deformed in the circumferential direction, the back foil is affected by friction with the bearing housing. Therefore, the back foil is easily deformed on the free end side, but is hardly deformed on the fixed end side. For this reason, a difference in support rigidity occurs between the free end side and the fixed end side, and it becomes difficult to obtain a uniform support rigidity for the entire bearing.
Therefore, since the back foil is composed of a plurality of back foil pieces arranged along the circumferential direction of the bearing housing, the distance between the fixed end and the free end of the back foil piece is shortened, and the above-described free foil is formed. The difference in support rigidity between the end side and the fixed end side is reduced. Therefore, variation in support rigidity in the entire back foil is reduced.
In addition, since the back foil is constituted by a plurality of back foil pieces in this way, the engagement protrusion is engaged by passing the engagement protrusion of the intermediate foil piece through the gap formed between them. It can be easily engaged with the recess.

Further, in the radial foil bearing, the inner peripheral surface of the bearing housing has a depth between the engaging recesses facing each other and communicated with the engaging recesses toward the outer peripheral edge side of the bearing housing from the engaging recesses. A shallow engagement groove is formed. The engagement recess and the engagement groove include a pair of engagement arms that engage with the engagement recess, and the pair of engagement arms that engage with the engagement groove. And an engaging convex portion that protrudes from an inner peripheral surface of the bearing housing on a side opposite to the side engaging the engaging concave portion of the pair of engaging arms. The engaging member is engaged, and at the peripheral edge portions on both sides of the back foil, engagement notches that engage with the engaging projections are formed, respectively, and the engaging protrusions of the intermediate foil piece are The engagement recess through the engagement notch of the back foil. It is preferable to.
In this way, the engagement protrusions provided on the both end portions of the inner peripheral surface of the bearing housing are engaged with the engagement notches formed on the peripheral edges on both sides of the back foil, so that the back foil is Since it fixes to a housing, a back foil can be accommodated and fixed in a bearing housing, without performing spot welding and a bending process with respect to a back foil. Therefore, it is possible to prevent the top foil from being distorted by spot welding of the back foil or the influence of the back foil, and the distortion of the top foil is sufficiently reduced. Further, since the back foil is not required to be welded, it is possible to eliminate assembly defects and assembly variations due to poor welding.
Further, since the engagement protrusion of the intermediate foil piece is engaged with the engagement recess through the engagement notch of the back foil, the engagement protrusion can be easily engaged with the engagement recess. it can.
Furthermore, since the engaging arm of the locking member and the engaging protrusion of the intermediate foil piece are both engaged with the engaging recess, the position where the engaging arm and the engaging protruding piece are engaged respectively Compared with the case where it forms separately, the number of processes with respect to a bearing housing can be decreased.

Further, in the radial foil bearing, engagement notches communicating with the engagement recesses are respectively formed on both side peripheral portions of the back foil, and the engagement protrusion of the intermediate foil piece is formed on the back foil. It is preferable to engage with the engaging recess through the engaging notch.
In this way, by engaging the engagement protrusion of the intermediate foil piece with the engagement recess, not only the intermediate foil piece but also the back foil can be fixed to the bearing housing.
Further, since the back foil is fixed to the bearing housing by the intermediate foil piece in this way, the back foil can be accommodated and fixed in the bearing housing without performing spot welding or bending on the back foil. Therefore, it is possible to prevent the top foil from being distorted by spot welding of the back foil or the influence of the back foil, and the distortion of the top foil is sufficiently reduced. Further, since the back foil is not required to be welded, it is possible to eliminate assembly defects and assembly variations due to poor welding.

In the radial foil bearing, the back foil includes a plurality of back foil pieces arranged along the circumferential direction of the bearing housing, and the engagement foil is formed in each of the back foil pieces. It is preferable that
In this way, the distance between the fixed end and the free end of the back foil piece is shortened, and the above-described difference in support rigidity between the free end side and the fixed end side is reduced. Therefore, variation in support rigidity in the entire back foil is reduced.
Further, since the engagement notches are formed in the back foil pieces, the engagement protrusions can be easily engaged with the engagement recesses by passing the engagement protrusions of the intermediate foil pieces through the engagement notches. be able to.

Further, in the radial foil bearing, it is preferable that the engagement notch of the back foil piece is formed at a central portion in the circumferential direction of the back foil piece.
In this way, the difference in the support rigidity between the free end side and the fixed end side of each back foil piece is further reduced, and therefore the variation in the support rigidity of the entire back foil is further reduced.

In the radial foil bearing, it is preferable that a plurality of the intermediate foils are stacked.
In this way, the damping effect obtained by the friction caused by the slip between the intermediate foils is added, so that the damping effect by the radial foil bearing is further enhanced.

According to the radial foil bearing of the present invention, the intermediate foil is constituted by a plurality of intermediate foil pieces arranged along the circumferential direction of the bearing housing. Therefore, the intermediate foil piece is provided between each intermediate foil piece and the back foil and the top foil. Thus, slipping can easily occur, and therefore, the damping effect due to friction caused by sliding can be increased.
In addition, since the intermediate foil is accommodated and fixed in the bearing housing without spot welding or large bending work on each intermediate foil piece, the top foil is distorted by the influence of the distortion of the intermediate foil. Can be prevented. Therefore, the distortion of the top foil is sufficiently reduced, and as a result, good performance as designed can be obtained with respect to the load capacity and dynamic characteristics (rigidity and damping) of the bearing.

It is a mimetic diagram showing an example of a turbo machine to which a radial foil bearing concerning the present invention is applied. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of 1st Embodiment of the radial foil bearing which concerns on this invention, (a) is a side view of a radial foil bearing, (b) is a figure which shows the principal part of the internal peripheral surface of a bearing housing. . (A) is an exploded perspective view of the main part of the radial foil bearing shown in FIG. 2 (a), (b) is a plan view showing a state in which a fixture is fitted in the through groove, and (c) is in the through groove. It is a sectional side view which shows the state which the fixing tool has fitted. (A) is a principal part disassembled perspective view of the radial foil bearing shown to Fig.2 (a), (b) is AA arrow sectional drawing of Fig.2 (a). 2A is an exploded perspective view of the main part of the radial foil bearing shown in FIG. 2A, FIG. 2B is a plan view of the intermediate foil piece, FIG. 2C is a side view of the intermediate foil piece, and FIG. It is CC sectional view taken on the line of (a). (A) is the side view which shows the main part of Fig.2 (a) planarized typically, (b) is the BB arrow directional view of (a). (A) is a development view of the top foil, and (b) is a development side view of the top foil. It is a principal part enlarged view of Fig.2 (a). It is a figure which shows 2nd Embodiment of the radial foil bearing which concerns on this invention, (a) is a side view of a radial foil bearing, (b) is a side view which planarizes the principal part of (a) and shows typically. is there. (A) is a principal part disassembled perspective view of the radial foil bearing shown to Fig.9 (a), (b) is DD sectional view taken on the line of FIG.9 (a). It is a figure which shows 3rd Embodiment of the radial foil bearing which concerns on this invention, (a) is a side view of a radial foil bearing, (b) is a side view which planarizes the principal part of (a) and shows typically. is there. (A) is a principal part disassembled perspective view of the radial foil bearing shown to Fig.11 (a), (b) is the EE arrow sectional drawing of Fig.11 (a). It is a principal part disassembled perspective view which shows the modification of the radial foil bearing of 3rd Embodiment.

  Hereinafter, a radial foil bearing of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  FIG. 1 is a side view showing an example of a turbo machine to which a radial foil bearing of the present invention is applied. In FIG. 1, reference numeral 1 denotes a rotary shaft, 2 denotes an impeller provided at a tip portion of the rotary shaft, and 3 denotes a main shaft. It is a radial foil bearing which concerns on invention. Although only one radial foil bearing is shown in FIG. 1, normally, two radial foil bearings are provided in the axial direction of the rotating shaft 1 to constitute a support structure for the rotating shaft 1. . Accordingly, it is assumed that two radial foil bearings 3 are also provided in the present embodiment.

A thrust collar 4 is fixed to the rotary shaft 1 on the side where the impeller 2 is formed, and a thrust bearing 5 is disposed on each side of the thrust collar 4 so as to face the thrust collar 4. ing.
The impeller 2 is disposed in the housing 6 on the stationary side, and has a tip clearance 7 between the impeller 2 and the housing 6.
A radial foil bearing 3 is externally attached to the rotary shaft 1 on the center side of the thrust collar 4.

“First Embodiment”
FIGS. 2A and 2B are views showing a first embodiment of a radial foil bearing applied to the turbomachine having such a configuration. The radial foil bearing 3 according to the first embodiment is a cylindrical member that is externally attached to the rotating shaft 1 and supports the rotating shaft 1 as shown in FIG. A cylindrical top foil 9, an intermediate foil 10 disposed radially outside the top foil 9, a back foil 11 disposed radially outside the intermediate foil 10, and a diameter of the back foil 11 And a bearing housing 12 disposed on the outer side in the direction.

  The bearing housing 12 is made of a metal and has a cylindrical shape that constitutes the outermost portion of the radial foil bearing 3, and the back foil 11, the intermediate foil 10, and the top foil 9 are accommodated therein. A through groove 13 is formed in the bearing housing 12 along the axial direction of the bearing housing 12 on the inner peripheral surface thereof. That is, as shown in FIG. 2B, which shows the main part of the inner peripheral surface of the bearing housing 12, the inner peripheral surface of the bearing housing 12 is continuously connected from one end to the other end in the axial direction of the bearing housing 12. A through groove 13 is formed along the entire length. The through groove 13 has the same length as that of the bearing housing 12 and has an opening width of about 3 mm to 5 mm and a depth of about 1.5 mm to 2.5 mm.

  Further, locking grooves 14 are formed at both ends of the through groove 13 so as to communicate with the through groove 13. As shown in FIG. 3A, which is an exploded perspective view of the main part of the radial foil bearing 3, the locking groove 14 is formed by cutting out both side surfaces of the bearing housing 12. It is formed from the inner periphery toward the outer periphery along the thickness direction. In the present embodiment, the width of the locking groove 14 is made sufficiently wider than the width of the through groove 13 so that the locking groove 14 is reliably communicated with the through groove 13.

  The through groove 13 is formed with a locking recess 15 on each of its inner side surfaces. These locking recesses 15 are groove-like ones formed in the entire length along the length direction of the through-groove 13, and in the present embodiment, the U-shaped cross section having a maximum depth of about 0.2 to 0.3 mm. It is formed in a shape (semi-arc shape). Further, these locking recesses 15 are formed at a depth position within 1 mm from the opening side of the through groove 13, for example, from the inner peripheral surface of the bearing housing 12. Thereby, the latching recessed part 15 can latch the front-end | tip part of the convex part of the top foil 9, so that it may mention later.

  Here, in order to form the through groove 13 and the locking recess 15, wire-cut electric discharge machining is preferably used. That is, when forming a continuous groove from one end to the other end in the axial direction of the bearing housing 12 such as the through groove 13 and the groove-shaped locking recess 15, the outer shape of the cross-sectional shape is formed by wire-cut electric discharge machining. By moving the wire so that it can be traced, each groove can be formed easily and accurately. In particular, in the present embodiment, the through groove 13 and the locking recesses 15 on both side surfaces thereof can be easily formed by a series of processing. Thus, by adopting wire cut electric discharge machining in this way, the through groove 13 And the processing cost of the latching recessed part 15 can be restrained sufficiently low.

  Moreover, since the groove | channel which continues from the outer surface side of the bearing housing 12 also to the inner surface side is formed also about the latching groove | channel 14, the process cost can be suppressed low enough by employ | adopting wire cut electric discharge machining. However, since the locking groove 14 does not particularly require processing accuracy, cutting by an end mill or the like can be employed.

  A fixing tool 16 is fitted and locked in the through groove 13 and the locking groove 14. The fixing tool 16 is shown in FIG. 3A, FIG. 3B which is a plan view of the through groove 13 and the fixing tool 16, and FIG. 3C which is a side sectional view of the through groove 13 and the fixing tool 16. Thus, a rod-like (quadrangular columnar) base portion 17 that is fitted and accommodated in the through groove 13, and a pair of bent pieces 18 that are formed at both ends of the base portion 17 and are engaged with the engagement grooves 14, 14, 18 and two partition wall pieces 19 formed at the center of the base portion 17 and projecting to the opposite side of the bent piece 18.

  The base portion 17 is formed with a height of about 0.5 to 1.5 mm, and is formed so that its upper surface (surface on the partition piece 19 side) sinks about 1 mm from the opening of the through groove 13. The bent piece 18 is formed to have a length substantially equal to the distance between the bottom surface of the through groove 13 and the outer peripheral surface of the bearing housing 12, thereby abutting the locking groove 14 with a sufficient area and bearing. It does not protrude from the outer peripheral surface of the housing 12.

  Here, a restriction portion is formed by the bent pieces 18 and 18 and the locking grooves 14 and 14 provided in communication with the through groove 13. That is, the pair of bent pieces 18, 18 are respectively locked in the locking grooves 14, 14 provided at both ends of the through groove 13, so that the bearing housing 12 is sandwiched between the pair of bent pieces 18, 18. Thus, the fixture 16 is restricted from moving in the length direction of the through groove 13 (the axial direction of the bearing housing 12), and does not substantially move except for the clearance.

  As shown in FIGS. 3B and 3C, the partition wall piece 19 is formed at two positions that divide the base portion 17 into approximately three equal parts, and thus the through groove 13 approximately into three equal parts. It is formed so as to be at the same level as the opening position of the through groove 13 or slightly protrude from the through groove 13. For example, you may make it protrude about half the height of the back foil 11. FIG. The partition groove 19 divides the through groove 13 substantially in the length direction thereof, so that three engagement grooves 20 are formed in the through groove 13 by the fixture 16.

That is, the three engaging grooves 20 can be easily formed by fitting the fixing tool 16 into the locking groove 14 and the through groove 13 from the inner peripheral surface side of the bearing housing 12 and locking them. These engaging grooves 20 have a depth of about 1 mm, and the locking recesses 15 are opened on both inner side surfaces thereof.
The fixture 16 can be formed by wire-cut electric discharge machining of a metal plate made of stainless steel having a thickness of about 3 to 4 mm, for example.

  In addition, as shown in FIG. 2A, the bearing housing 12 is formed with an engaging projection 33 a for locking a back foil 11 described later by a locking member 30. That is, as shown in FIG. 4A, which is an exploded perspective view of the main part of the radial foil bearing 3, grooves on both side surfaces of the bearing housing 12 extend from the inner peripheral edge to the outer peripheral edge of the bearing housing 12, respectively. First engaging recesses 31 are formed so as to face each other. As shown in FIG. 2A, the first engaging recess 31 is formed at a position where the side surface of the bearing housing 12 is substantially divided into three in the circumferential direction in the present embodiment. The locking member 30 is locked to the first engagement recesses 31. In the present embodiment, the through groove 13 is disposed between two first engaging recesses 31 of the three first engaging recesses 31 when viewed from one side surface of the bearing housing 17. Has been.

  Further, on the inner peripheral surface of the bearing housing 12, a groove 32 communicating with the first engagement recesses 31, 31 is formed between the first engagement recesses 31, 31 facing each other as shown in FIG. Has been. The depth of the groove 32 is shallower than the depth of the first engagement recess 31, that is, the depth toward the outer surface side of the bearing housing 12 (which is equal to the thickness of the bearing housing 12 in this embodiment). ing. Thereby, in this embodiment, the level | step-difference part (not shown) is formed between the 1st engagement recessed part 31 and the groove | channel 32. FIG.

  The locking member 30 is locked to the first engagement recesses 31 and 31 and the groove 32. The locking member 30 has a pair of engaging arms 33 that engage with the first engaging recesses 31, 31 and a connecting portion 34 that connects the engaging arms 33, 33, and has an H shape. It is formed. As shown in FIG. 4B, which is a cross-sectional view taken along the line AA in FIG. 2A, the connecting portion 34 engages with the groove 32 and is accommodated in the groove 32. It is formed so as not to protrude outside. Specifically, the depth of the groove 32 is about 1 mm to 2 mm, and therefore the height of the connecting portion 34 is also about 1 mm to 2 mm.

  The pair of engagement arms 33 are formed to extend in the vertical direction with respect to the connecting portion 34, thereby forming the locking member 30 in an H shape as described above. The portions extending above the engagement arms 33, that is, the side opposite to the side engaged with the first engagement recess 31, protrudes from the inner peripheral surface of the bearing housing 12, whereby a back foil piece 11a described later is provided. It is the engagement convex part 33a engaged with this engagement notch 11d.

  Further, the portion extending to the lower side of the engagement arm 33 is locked to the step portion between the first engagement recess 31 and the groove 32 described above. Thereby, the locking member 30 is restricted from moving in the axial direction with respect to the bearing housing 12.

  Note that the engaging arm 33 and the connecting portion 34 of the locking member 30 may have a quadrangular prism shape as shown in FIG. 4A or a cylindrical shape (round bar shape). The length is about 0.3 to 0.5 mm. Such a locking member 30 can be formed, for example, by etching a metal foil made of stainless steel or the like having a thickness of less than 0.5 mm into an H shape or wire-cut electric discharge machining.

Further, the grooves 32 can be formed by wire-cut electric discharge machining in the same manner as the through grooves 13. Further, the first engaging recess 31 can be processed by wire-cut electric discharge machining, cutting by an end mill, or the like in the same manner as the locking groove 14. That is, the through groove 13 and the groove 32 can be processed continuously by wire cut electric discharge machining. Similarly, the locking groove 14 and the first engagement recess 31 can be processed by wire cut electric discharge machining or the like. It can be processed continuously. Therefore, the processing cost of the bearing housing 12 can be reduced.
After forming the groove 32 and the first engagement recess 31 in this manner, the locking member 30 is fitted into the first engagement recess 31 and the groove 32 from the inner peripheral surface side of the bearing housing 12 and locked. The engaging convex portion 33a can be easily formed.

  Further, as shown in FIG. 2A, the bearing housing 12 is formed with second engaging recesses 35 for holding an intermediate foil piece 10a described later on both side surfaces thereof. The second engagement recess 35 functions as an engagement recess in the present invention. As shown in FIG. 5 (a), which is an exploded perspective view of a main part of the radial foil bearing 3, the second engagement recess 35 is formed from the outer peripheral edge of the bearing housing 12. It is formed to extend in a groove shape to the periphery. As shown in FIG. 2A, the second engagement recess 35 is formed in a pair facing both sides of the bearing housing 12. In the present embodiment, a total of three pairs of such second engaging recesses 35 are formed, and these second engaging recesses 35 are respectively formed at positions where the side surface of the bearing housing 12 is substantially divided into three in the circumferential direction. Has been.

Further, the second engagement recesses 35 are formed and arranged in a state shifted by a half pitch with respect to the first engagement recesses 31. That is, one of the three pairs of second engagement recesses 35 is disposed on one side of the through groove 13, and the other two are central portions between the adjacent first engagement recesses 31, 31. Is arranged.
The second engaging recess 35 can also be processed by wire cut electric discharge machining in the same manner as the locking groove 14 and the first engaging recess 31. That is, the locking groove 14, the first engagement recess 31 and the second engagement recess 35 can be continuously processed by wire cut electric discharge machining. Therefore, the processing cost of the bearing housing 12 can be reduced. Further, a laser method can be used instead of the wire cut electric discharge machining.

  The back foil 11 is formed of a foil (thin plate) and elastically supports the intermediate foil 10 and the top foil 9. Examples of such a back foil 11 include a bump foil, a spring foil described in Japanese Patent Application Laid-Open No. 2006-57652 and Japanese Patent Application Laid-Open No. 2004-270904, and Japanese Patent Application Laid-Open No. 2009-299748. A back foil or the like is used. In the present embodiment, a bump foil is used as the back foil 11. However, it goes without saying that the spring foil or the back foil may be used as the back foil of the present invention.

  In the present embodiment, the back foil (bump foil) 11 is constituted by three (a plurality of) back foil pieces 11 a arranged along the circumferential direction of the bearing housing 12. These back foil pieces 11a are formed so that a foil (thin plate) is formed into a corrugated plate shape, and the side surfaces are formed into a substantially arc shape as a whole, and all three pieces are formed in the same shape and size. Therefore, these back foil pieces 11 a are arranged by dividing the inner peripheral surface of the bearing housing 12 into approximately three parts.

  Further, these back foil pieces 11a are arranged with a certain gap at a position sandwiching the through groove 13, and at other positions, their end portions are arranged at a predetermined interval. And the said 2nd engagement recessed part 35 is formed in the position which opened this predetermined space | interval. A second engagement recess 35 is also formed on one side of the through groove 13 at a position sandwiching the through groove 13. With such a configuration, the three back foil pieces 11 a are formed in a substantially cylindrical shape as a whole, and are arranged in the circumferential direction of the top foil 9 via the intermediate foil 10.

  Further, the back foil piece 11a formed in the corrugated plate shape as described above is a circumferential direction of the bearing housing 12 as shown in FIG. A flat valley portion 11b in contact with the bearing housing 12 and a curved peak portion 11c in contact with the intermediate foil 10 (intermediate foil piece 10a) are alternately formed. As a result, the back foil piece 11a elastically supports the top foil 9 via the intermediate foil piece 10a, in particular, by the crest portion 11c contacting the intermediate foil piece 10a (intermediate foil 10). Further, a fluid passage is formed by the crests 11 c and the troughs 11 b in the axial direction of the radial foil bearing 3.

  Further, as shown in FIG. 6B, which is a view taken along the line B-B of FIG. 6A, these back foil pieces 11a have respective circumferential center portions (along the circumferential direction of the bearing housing 12). Engagement notches 11d are formed at the peripheral edge portions on both sides of the central portion in the direction. The engagement notch 11d is formed in the valley portion 11b of the back foil piece 11a as shown in FIG. 6A, and the valley portion 11b composed of a flat portion formed between the mountain portions 11c and 11c It is formed by cutting out in a rectangular shape from the side periphery to the inside.

  The engaging notch 11d is formed at a position corresponding to the engaging convex portion 33a of the engaging member 30 provided in the bearing housing 12, that is, a position overlapping the engaging convex portion 33a. The engaging protrusions 33a are formed to have substantially the same vertical and horizontal width so as to engage with the engaging protrusions 33a. Specifically, the lateral width along the circumferential direction of the bearing housing 12 is about 0.2 mm to 0.4 mm, and the vertical width along the axial direction is about 1 mm to 2 mm.

In addition, about formation of the engagement notch 11d, it is preferable to perform a foil by an etching process or an electrical discharge process so that a burr | flash does not generate | occur | produce and the distortion by a process does not arise. That is, it is preferable to form the back foil piece 11a by forming the engagement notch 11d in the foil by etching process or electric discharge process and then performing press molding to form the peak part 11c or the valley part 11b.
Under such a configuration, the engagement convex portion 33a of the bearing housing 12 (the engagement arm 33 of the locking member 30) has a back foil piece as shown in FIGS. 4 (a) and 6 (a). The engagement notch 11d of 11a is engaged.

  In this way, the engagement notch 11d of the back foil piece 11a is engaged with the engagement convex portion 33a extending to the upper side of the engagement arm 33, and in this state, three backs on the inner peripheral surface of the bearing housing 12 are engaged. Since the foil piece 11a is disposed, the locking member 30 is prevented from falling off the bearing housing 12 particularly when the connecting portion 34 is pressed by the back foil piece 11a.

  As shown in FIG. 2 (a), the intermediate foil 10 is disposed between the back foil 11 and the top foil 9 made of three back foil pieces 11a. Are formed by three intermediate foil pieces 10a. As shown in FIGS. 5B and 5C, the intermediate foil piece 10a is formed in a substantially rectangular shape, and each of the intermediate foil pieces 10a is predetermined so that a substantially cylindrical shape is formed by the three intermediate foil pieces 10a. By being curved with a curvature, it is formed in the intermediate foil piece 10a having an arc shape in a side view. In addition, projecting pieces indicated by two-dot chain lines are formed at both ends on one short side, and the projecting pieces are bent substantially at right angles, whereby an engaging projecting piece 10b is formed.

  And the engagement protrusion 10b formed in this way is a gap formed between the three back foil pieces 11a as shown in FIGS. 2 (a), 5 (a), and 6 (a). By engaging with the second engagement recess 35 of the bearing housing 12 through the intermediate foil piece 10a, as shown in FIG. 5 (d), which is a cross-sectional view taken along the line CC of FIG. 2 (a). Further, the bearing housing 12 holds the back foil piece 11a. In this way, the intermediate foil piece 10a held by the bearing housing 12 is formed in the second engaging recess 35 so that the engaging protrusions 10b formed on both sides of the intermediate foil piece 10b sandwich both side surfaces of the bearing housing 12. Is engaged. Therefore, even when an unexpected external force is applied to the radial foil bearing 3 due to the shaft shake of the rotary shaft 1, the intermediate foil piece 10a does not rotate in the bearing housing 12, and further in the bearing housing 12 in the axial direction. Since it does not move, it does not fall off from the bearing 3.

  As shown in FIG. 2 (a), the top foil 9 is wound in a cylindrical shape along the inner surface of the intermediate foil 10 composed of three intermediate foil pieces 10a, and is formed on one end side. 21 a and the convex portion 21 b formed on the other end side are arranged to engage with the engaging groove 20 in the through groove 13 formed in the bearing housing 12, respectively. As shown in FIG. 7A, which is a development view of the top foil 9, a rectangular metal foil having a long side in the bearing circumferential direction and a short side in the bearing length direction is a side view thereof. 7 (b) is formed by being wound in a cylindrical shape in the arrow direction (long side length direction: bearing circumferential direction).

  As shown in FIG. 7A, the top foil 9 has a first concavo-convex portion 23a having one convex portion 21a and two concave portions 22a on one side (short side). And a second concavo-convex portion 23b having two convex portions 21b and one concave portion 22b is formed on the other side (short side) opposite to the one side (short side). Has been. The concave portion 22b of the second concave-convex portion 23b is formed corresponding to the convex portion 21a of the first concave-convex portion 23a, and the concave portion 22a of the first concave-convex portion 23a corresponds to the convex portion 21b of the second concave-convex portion 23b. Is formed.

  That is, when the top foil 9 is wound in a cylindrical shape so that the first uneven portion 23a and the second uneven portion 23b overlap with each other, the recessed portion 22b of the second uneven portion 23b has a protruding portion 21a. Is formed to pass through. Similarly, the concave portion 22a of the first uneven portion 23a is formed so that the convex portion 21b passes through the concave portion 22a when the top foil 9 is wound in a cylindrical shape. The protrusions 21a and 21b are formed so that the width thereof substantially coincides with the length of the engagement groove 20 formed by the through groove 13 and the fixture 16.

  The convex portions 21a and 21b that have passed through the concave portions 22b and 22a are respectively drawn out toward the bearing housing 12 as shown in FIG. 2A, and the tip portions thereof are engaged with the engaging grooves 20 of the bearing housing 12. . In this embodiment, as shown in FIG. 8 which is an enlarged view of the main part of FIG. 2A, the projecting portions 21a and 21b are engaged with the tip portions thereof being inserted into the engaging grooves 20 in the through grooves 13, respectively. After being combined, they are further placed in the locking recess 15 and locked there. As a result, the top foil 9 is arranged so that its movement in the circumferential direction is restricted and its movement amount is small.

  That is, the convex portions 21 a and 21 b are arranged so that the tip end side faces the inner surface of the locking recess 15 without the tips of the projections being strongly abutted against the inner surface of the locking recess 15. Therefore, during the steady operation of the rotating shaft 1, the convex portions 21 a and 21 b do not receive a large reaction force from the locking concave portion 15 or the engaging groove 20, so that the top foil 9 is not distorted. Further, even when an unexpected external force is applied to the radial foil bearing 3 due to the shaft shake of the rotating shaft 1, the top foil 9 does not rotate in the bearing housing 12, and the bearing housing 12 and the rotating shaft 1 are further rotated. It is designed not to fall out.

  That is, when an unexpected external force is applied, the convex portions 21a and 21b are firmly locked to the inner surface of the locking concave portion 15 so that the convex portions 21a and 21b are disengaged from the locking concave portion 15, and further the engagement groove. Therefore, the top foil 9 is rotated or excessively deformed, and the convex portions 21a and 21b come out of the concave portions 22b and 22a, and the top foil 9 is detached from the bearing housing 12. Is prevented.

  Further, the protrusions 21 a and 21 b are restricted from moving in the axial direction by the partition piece 19 of the fixture 16 that defines the engagement groove 20. That is, both sides of the convex portion 21a are restricted by the partition piece 19, so that the movement in the axial direction is restricted on the first concave and convex portion 23a side where the convex portion 21a is formed. In addition, the two convex portions 21b are respectively regulated on the one side by the partition piece 19 and in the opposite directions to each other, so that the second concave and convex portion 23b side that forms these two convex portions 21b is also a shaft. Movement in the direction is restricted. Thus, since the top foil 9 is restricted from moving in the axial direction of the bearing housing 12, the top foil 9 is prevented from jumping out from the bearing housing 12.

  Moreover, as shown in FIG.7 (b), the top foil 9 has the side (one side) in which the 1st uneven part 23a was formed, and the side (the other side) in which the 2nd uneven part 23b was formed. In addition, a thin portion 24 that is thinner (thin) than the central portion between them is formed. As shown in FIG. 2A, these thin portions 24 are thinned (thinned) so that the outer peripheral surface (the surface on the bearing housing 12 side) is recessed from the outer peripheral surface of the central portion. Is formed.

In order to form the thin-walled portion 24, both ends of the top foil 9 are controlled to the order of 10 μm to form a desired thickness (thinness) by, for example, etching. Specifically, when the bearing diameter is 35 mm, when the thickness of the top foil 9 is 100 μm, the thickness of the thin portion 24 is about 80 μm. In such an etching process, the stress generated in the top foil 9 is extremely small as compared with the bending process, and therefore, the top foil 9 is hardly distorted.
Moreover, the circumferential length L of the thin portion 24 shown in FIG. 7B is equal to the through groove 13 and one end crest of the bump foil (back foil) 11 as shown in FIG. The length corresponds to the minute.

  Since the thin portions 24 are formed at both end portions of the top foil 9 as described above, these both end portions (thin wall portions 24) are easily elastically deformed. Therefore, these both end portions are curved surfaces constituting the inner peripheral surface of the bearing housing 12. It becomes a curved surface following. As a result, the top foil 9 hardly generates a force (local preload) for tightening the rotary shaft 1 at both ends thereof.

  Further, since the outer peripheral surface of both ends of the top foil 9 is thinned so as to be recessed from the outer peripheral surface of the central portion, and the thin portion 24 is formed, the outer peripheral surface side through the intermediate foil 10 A gap is formed between the end of the back foil 11 and the back of the back foil 11. Thereby, in the thin part 24, it is reliably prevented that the force (local preload) which tightens the rotating shaft 1 arises. The circumferential length L of the thin portion 24 is a length corresponding to up to about three through-grooves 13 and the peaks of the end of the bump foil 11 instead of the example shown in FIG. It may be good.

Next, the operation of the radial foil bearing 3 having such a configuration will be described.
In a state where the rotating shaft 1 is stopped, the top foil 9 is urged toward the rotating shaft 1 by the back foil 11 (three back foil pieces 11a) via the intermediate file 10 (three intermediate foil pieces 10a). It is in close contact with the rotating shaft 1. In the present embodiment, since both end portions of the top foil 9 are the thin portions 24, the thin portion 24 hardly generates a force (local preload) for tightening the rotating shaft 1.

  When the rotary shaft 1 is started in the direction of the arrow P in FIG. 2A, it starts rotating at a low speed first, and then gradually accelerates and rotates at a high speed. Then, as indicated by an arrow Q in FIG. 2A, ambient fluid is drawn from one end side of the top foil 9, the intermediate foil 10, and the bump foil 11, and flows between the top foil 9 and the rotating shaft 1. To do. Thereby, a fluid lubricating film is formed between the top foil 9 and the rotating shaft 1.

  The film pressure of the fluid lubricating film acts on the top foil 9 and presses the individual peaks 11 c of the back foil piece 11 a through the intermediate foil 10 in contact with the top foil 9. Then, when the back foil piece 11a is pressed by the intermediate foil 10, the crest portion 11c is pushed and widened, so that the back foil piece 11a tries to move on the bearing housing 12 in the circumferential direction. That is, since the back foil piece 11a (back foil 11) elastically supports the top foil 9 via the intermediate foil 10, when it receives a load from the top foil 9, it is deformed in its circumferential direction. The top foil 9 and the intermediate foil 10 are allowed to bend and are supported.

  However, as shown in FIGS. 4 (a) and 4 (b), the engaging protrusion 33a of the locking member 30 is engaged with the engaging notch 11d provided on the side peripheral edge of the back foil piece 11a. Thus, the back foil piece 11 a is prevented from rotating in the circumferential direction on the inner peripheral surface of the bearing housing 12. Therefore, each peak portion 11c of the back foil piece 11a is deformed (moved) in the circumferential direction with the engagement notch 11d with which the engagement convex portion 33a is engaged as a fixed point (fixed end). The center of 11a itself does not deviate from the fixed position.

  Further, when the back foil piece 11a is deformed (moved) in the circumferential direction, the back foil piece 11a is affected by friction between the bearing housing 12 and the intermediate foil 10, and therefore is easily deformed (movable easily) at both ends thereof, that is, the free end side. However, it is difficult to deform on the fixed point (fixed end) side. Therefore, a difference occurs in the support rigidity by the back foil piece 11a between the free end side and the fixed end side.

  However, in this embodiment, since the back foil 11 is divided into three back foil pieces 11a, the distance between the fixed end and the free end is smaller than when the back foil 11 is formed of a single foil. Due to the shortening, the difference in the support rigidity is reduced. Furthermore, the engagement notch 11d is formed in the center in the circumferential direction of the back foil piece 11a, and the fixing point by the engagement convex portion 33a is the center in the circumferential direction of the back foil piece 11a. Therefore, the difference in the support rigidity between the free end side and the fixed end side is further reduced.

Further, when the rotary shaft 1 rotates at a high speed, the engagement convex portion 33a also restrains the movement of the back foil piece 11a in the axial direction, so that even if an unexpected impact or the like is applied, the back foil piece 11a does not fall off from the bearing housing 12.
Similarly, the intermediate foil piece 10a is engaged with the second engaging recesses 35 formed on both side surfaces of the bearing housing 12 at the engaging protrusions 10b. Without rotating in the housing 12, the bearing housing 12 is not moved in the axial direction. Further, since the radial direction is covered with the top foil 9, the intermediate foil piece 10a is prevented from falling off the bearing 3 by functioning as a retaining member.

  Further, in a transient state until the fluid lubrication film is formed, solid friction is generated between the rotating shaft 1 and the top foil 9, and this becomes a resistance at the time of starting. However, as described above, there is no preloading at both ends of the top foil 9, and the top foil 9 on the side into which the surrounding fluid flows is a thin-walled portion 24 that is soft and rotates with the top foil 9. Since the space between the shaft 1 and the shaft 1 is easily opened, a fluid lubricating film is formed at an early stage when the rotating shaft 1 is started, and the rotating shaft 1 rotates in a non-contact state with respect to the top foil 9.

In such a radial foil bearing 3, since the intermediate foil 10 is disposed between the top foil 9 and the back foil 11, the rotary shaft 1 causes shaft vibration (self-excited vibration) during rotation. When this occurs, the accompanying film pressure fluctuation is transmitted from the top foil 9 to the back foil 11 (back foil piece 11a) via the intermediate foil 10 (intermediate foil piece 10a). At that time, the top foil 9 is caused to be slightly bent (varied according to the load) due to the load fluctuation, and thereby, between the top foil 9 and the intermediate foil 10 and between the intermediate foil 10 and the back foil 11. “Slip” occurs between them. This "slip" causes energy dissipation due to friction and attenuates membrane pressure fluctuations. That is, an attenuation effect is obtained. Accordingly, the axial vibration (self-excited vibration) can be suppressed by the damping effect, and the axial vibration can be easily settled.
Further, since the intermediate foil 10 is constituted by three (a plurality of) intermediate foil pieces 10 a arranged along the circumferential direction of the bearing housing 12, a single intermediate foil is wound around the bearing housing 12 once. Compared with the case where it arrange | positions, the said "slip" between the back foil 11 and the top foil 9 becomes difficult to be restrained, and the restraint location by friction reduces. Therefore, slipping is likely to occur between each intermediate foil piece 10a and the back foil 11 or the top foil 9, and the damping effect due to friction caused by sliding can be increased.

  Further, since the engagement protrusions 10b formed on the intermediate foil piece 10a are engaged with the second engagement recesses 35 formed on both side surfaces of the bearing housing 12, spot welding is performed on each intermediate foil piece 10a. The intermediate foil 10 made of the intermediate foil piece 10a can be accommodated and fixed in the bearing housing 12 without performing a large bending process. Therefore, it is possible to prevent the top foil 9 from being distorted due to spot welding of the intermediate foil 10 or the influence of the distortion of the intermediate foil 10, and the distortion of the top foil 9 can be sufficiently reduced. Since the distortion of the top foil 9 is sufficiently reduced as described above, good performance as designed can be obtained with respect to the load capacity and dynamic characteristics (rigidity and damping) of the bearing.

  Further, since the intermediate foil 10 and the back foil 11 are not required to be welded, it is possible to eliminate assembly defects and assembly variations due to poor welding, facilitating manufacturing, and improving assembly reproducibility. Thereby, cost reduction can be achieved. Further, when the intermediate foil piece 10a and the back foil piece 11a are damaged or worn out, the damaged or worn parts (the intermediate foil piece 10a and the back foil piece 11a) without exchanging the whole intermediate foil 10 or the entire back foil 11. You only need to replace it.

Further, since the back foil 11 is constituted by a plurality of back foil pieces 11a arranged along the circumferential direction of the bearing housing 12, the distance between the fixed end and the free end of the back foil piece 11a is shortened. The difference in support rigidity between the free end side and the fixed end side is reduced. Therefore, variation in the support rigidity in the entire back foil 11 can be reduced.
Further, since the engagement notch 11d of the back foil piece 11a is formed at the center in the circumferential direction of the back foil piece 11a, the support rigidity between the free end side and the fixed end side of each back foil piece 11a is increased. The difference is even smaller. Therefore, the variation in support rigidity in the entire back foil 11 can be further reduced.
Further, since the back foil 11 is constituted by the plurality of back foil pieces 11a as described above, the engagement protrusion 10b of the intermediate foil piece 10a is passed through a gap formed between them, thereby the engagement protrusion 10b. The piece 10 b can be easily engaged with the second engagement recess 35.

  Further, by engaging engagement notches 11d formed on both side peripheral portions of the back foil piece 11a with engagement protrusions 33a formed on both side ends of the inner peripheral surface of the bearing housing 12, the back foil piece is formed. Since 11 a is fixed to the bearing housing 12, the back foil piece 11 a can be accommodated and fixed in the bearing housing 12 without performing spot welding or bending on the back foil piece 11 a. Therefore, it is possible to prevent the top foil 9 from being distorted due to spot welding of the back foil 11 (back foil piece 11a) or the influence of the distortion of the back foil 11, and the distortion of the top foil 9 can be sufficiently reduced.

Further, since the through groove 13 is continuously formed from one end to the other end along the axial direction of the bearing housing 12, the through groove 13 can be easily formed by discharge wire cutting, and therefore the machining thereof is performed. Cost can be kept low.
Further, even if an axial shift is likely to occur between the top foil 9 and the bearing housing 12, the convex portion 21a that engages with the engagement groove 20 formed by dividing the through groove 13 in the length direction. , 21b are restricted by the end portion (partition piece 19) of the engagement groove 20 and the movement thereof is stopped, so that the shift can be prevented.

Further, a locking recess 15 is formed on the inner side surface of the through groove 13, and the tips of the protrusions 21a, 21b of the top foil 9 are locked to the locking recess 15, so that the protrusion 21a, 21b can be positioned and locked easily, and the assembly reproducibility of the top foil 9 can be improved.
Further, with respect to the top foil 9, only the formation of the concavo-convex portions 23a and 23b by the etching process is increased, and the conventional spot welding and bending process that generates distortion can be eliminated. Therefore, the difficulty of manufacture can be reduced and the manufacturing cost can be reduced.
Further, since there is no welding of the top foil 9 to the bearing housing 12, there is no assembly failure due to welding failure or variation in assembly. Therefore, reproducibility is improved and the mass productivity is excellent.

Moreover, since the thin part 24 is formed in the both ends of the top foil 9, the top foil 9 does not generate | occur | produce the force (local preload) which clamps the rotating shaft 1 also in these both ends. Therefore, it is possible to prevent the starting torque from being increased by preloading, and the heat generated during operation from being higher than the set value.
Further, since the thin portions 24 are formed at both end portions of the top foil 9, for example, a heat treatment step for adapting the both end portions of the top foil to the inner curved surface (inner peripheral surface) of the bearing housing is not required. become.
Further, since the thin portions 24 are formed at both ends of the top foil 9, the end portion side of the top foil 9 on the side into which the surrounding fluid flows is soft, so that the surrounding fluid rotates with the top foil 9 as described above. It becomes easy to flow in between the shaft 1. Therefore, the fluid lubricating film is formed at a lower rotational speed, and the startability is improved.

“Second Embodiment”
Next, a second embodiment of the radial foil bearing of the present invention will be described. FIGS. 9A, 9B, 10A, and 10B are views showing a second embodiment of the radial foil bearing applied to the turbomachine shown in FIG. 1, and FIG. ) Middle reference numeral 40 is a radial foil bearing. The radial foil bearing 40 is different from the radial foil bearing 3 shown in FIG. 2A in that the intermediate foil 41 is composed of six intermediate foil pieces 41a and the engagement protrusions 41b of the intermediate foil piece 41a. The engagement point is engaged with the first engagement recess 31 with which the engagement arm 33 of the locking member 30 is engaged.

  In the present embodiment, the bearing housing 42 is not formed with the second engagement recess 35, and only the first engagement recess 31 that functions as the engagement recess in the present invention is formed. In addition, about the structure of the penetration groove | channel 13 for engaging the convex parts 21a and 21b of the top foil 9, the latching groove | channel 14, and the fixing tool 16, it is the same as 1st Embodiment.

  The intermediate foil piece 41a constituting the intermediate foil 41 has substantially the same configuration as the intermediate foil piece 10a of the first embodiment shown in FIGS. 5B and 5C, and the difference is the bearing housing 42. The length along the circumferential direction is that it is formed to be approximately half the length of the intermediate foil piece 10a as shown in FIG. 9 (a). That is, the intermediate foil piece 41a of the present embodiment is also formed in a substantially rectangular shape like the one shown in FIGS. 5B and 5C, and is substantially cylindrical by the six intermediate foil pieces 41a. Each of them is curved with a predetermined curvature so as to form a shape, so that it is formed into an arcuate shape in a side view having a pair of engaging protrusions 41b.

  In the present embodiment, these intermediate foil pieces 41a have their engaging projections 41b engaged with the first engaging recesses 31 through the engagement notches 11d of the back foil piece 11a as shown in FIG. 9B. doing. That is, the intermediate foil pieces 41a are arranged such that a pair of adjacent ones in the circumferential direction of the bearing housing 42 are opposed to each other as shown in FIG. 10 (a). These engagement protrusions 41b are engaged with the first engagement recesses 31 through the engagement notches 11d. At this time, the pair of engaging protrusions 41b are arranged on both sides of the engaging arm 33 of the locking member 30 that locks in the first engaging recess 31, as shown in FIG. It is engaged between the side surface and the inner side surface forming the first engaging recess 31.

Here, in the present embodiment, as shown in FIG. 10A, the groove 32 for locking the locking member 30 and the first engagement recess 31 for engaging the engagement arm 33 are respectively Are different in width (width along the circumferential direction of the bearing housing 42). That is, when the thickness of the locking member 30 and its engaging arm 33 and the thickness of the connecting portion 34 are a, and the thickness of the intermediate foil piece 41a (the thickness of the engaging projection piece 41b) is b, the groove 32 is obtained. The width of the first engaging recess 31 of the bearing housing 42 is not less than (a + 2b). Further, the width of the engagement notch 11d of the back foil piece 11a is substantially (a + 2b). Accordingly, as shown in FIG. 10B, which is a cross-sectional view taken along the line D-D in FIG. 9A, the coupling portion 34 of the locking member 30 is engaged with the groove 32. . Further, the engagement arm 33 (engagement convex portion 33a) of the locking member 30 is engaged with the engagement notch 11d, and a pair of engagement protrusions 41b are engaged. Further, the engagement arm 33 of the locking member 30 is engaged with the first engagement recess 31, and the pair of engagement protrusions 41 b are engaged.
The above dimensions can be changed as appropriate. For example, the thickness of the engagement arm 33 is reduced to (a-2b) by etching, and the width of the first engagement recess 31 is slightly smaller than a. The width of the engagement notch 11d may be a.

In such a radial foil bearing 40, in addition to the effect obtained by the radial foil bearing 3 of the first embodiment, the processing of the bearing housing 42 is performed by eliminating the processing of the second engagement recess 35. The effect that it can be made easy is acquired.
Further, since the intermediate foil 41 is composed of six intermediate foil pieces 41a instead of three, the above-described frictional restraint points are further reduced, and the intermediate foil pieces 41a are connected to the back foil 11 and the top foil 9 between them. Thus, slipping is more likely to occur, and the damping effect due to friction can be further increased.
Further, the back foil 11a can be fixed to the bearing housing 42 by the intermediate foil piece 41a.

“Third Embodiment”
Next, a third embodiment of the radial foil bearing of the present invention will be described. 11 (a), 11 (b), 12 (a), and 12 (b) are views showing a third embodiment of the radial foil bearing applied to the turbo machine shown in FIG. ) Middle reference numeral 50 is a radial foil bearing. The radial foil bearing 50 is different from the radial foil bearing 40 shown in FIG. 9A in that the locking member 30 is eliminated and the back foil piece 11a is fixed to the bearing housing 51 by the intermediate foil piece 41a. It is.

  That is, in this embodiment, the groove 32 for locking the locking member 30 shown in the first embodiment or the second embodiment is not formed in the bearing housing 51, and the first engagement recess 31 is not formed. Only formed. Further, as shown in FIG. 11B, the intermediate foil piece 41a is engaged with the first engagement recess 31 through the engagement notch 11d of the back foil piece 11a. As shown in FIG. 12 (a), a pair of intermediate foil pieces 41a adjacent to each other in the circumferential direction of the bearing housing 42 are arranged so that the engaging protruding pieces 41b face each other, and these engaging protruding pieces 41b. Are respectively engaged with the first engagement recesses 31 through the engagement notches 11d. At this time, since the locking member 30 is not provided in this embodiment, only the pair of engagement protrusions 41b are engaged with the first engagement recess 31 as shown in FIG. Yes.

  Therefore, in this embodiment, as shown in FIG. 12A, the first engagement recess 31 has a width (in the circumferential direction of the bearing housing 51) as compared with the first engagement recess 31 shown in the second embodiment. (Width along) is sufficiently narrow. Specifically, the width is about twice the thickness b of the engaging protrusion 41b of the intermediate foil piece 41a. In addition, the width of the engagement notch 11d of the back foil piece 11a is preferably about twice as large as the thickness b of the engagement protrusion 41b. In addition, since the thickness b of the engagement protrusion 41b is usually very thin, 0.1 mm or less, the width of the first engagement recess 31 needs to be 0.2 mm or less. However, such a narrow width processing is difficult at present, and, for example, a high cost is required because a laser method is used. Therefore, in this embodiment, as shown in FIG. 13, it is preferable to use a plurality of intermediate foil pieces 41a by stacking a plurality of layers (two layers in FIG. 13). If multiple layers are formed in this way, the engagement protrusions 41b are also thickened accordingly, and the width of the first engagement recess 31 can be increased. Therefore, the processing of the first engaging recess 31 is facilitated, and the cost can be reduced accordingly.

  In such a radial foil bearing 40, in addition to the effects obtained by the radial foil bearing 3 of the second embodiment, the locking member 30 is not required, the number of parts and the number of assembling steps are reduced, and the grooves 32 are further formed. By eliminating the need for processing, the cost can be greatly reduced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, in the first embodiment and the second embodiment, only one (one layer) intermediate foil made of intermediate foil pieces is used, but a plurality of intermediate foils (intermediate foil pieces) are used as shown in FIG. Multiple layers may be stacked. Thus, by arranging the intermediate foil in a multilayer between the back foil and the top foil, it is obtained by friction generated by sliding between the top foil and the intermediate foil or between the intermediate foil and the back foil. A damping effect obtained by friction caused by slippage between the intermediate foils is added to the damping effect. Therefore, the shaft vibration (self-excited vibration) of the rotating shaft can be suppressed and the shaft vibration can be more easily settled.

  Here, in order to increase the damping capacity of the radial foil bearing, the multilayering of the intermediate foil is effective as described above. However, conventionally, since the intermediate foil is spot welded to the bearing housing, it is necessary to adjust the thickness of the intermediate foil to such an extent that the intermediate foil does not melt off by this welding, and therefore, the thickness of the intermediate foil is set to the same level as the top foil. For this reason, if a plurality of intermediate foils having such a thickness are stacked to form a multilayer structure, the rigidity of the bearing surface (the rigidity of the top foil and the intermediate foil combined) becomes too high, and the fluid lubrication film caused by the shaft vibration is increased. The bearing surface does not follow the film pressure fluctuation well. As a result, it becomes difficult to obtain an attenuation effect due to “slip” between the foils.

  On the other hand, in the embodiment, the intermediate foil is fixed between the back foil and the top foil by engaging the engagement protrusion with the engagement recess without welding the intermediate foil to the bearing housing. The intermediate foil can be formed with a sufficiently thin thickness with respect to the top foil. Therefore, it is possible to make the bearing surface multi-layered while suppressing the rigidity of the bearing surface to an appropriate height (strength).

  In the first embodiment and the second embodiment, the engaging convex portion 33a to be engaged with the engaging notch 11d of the back foil piece 11a is not formed by the engaging arm 33 of the locking member 30, and the bearing is formed. The engaging convex portion 33 a may be formed directly on the inner peripheral surface of the housing 12. In that case, particularly in the second embodiment, a groove-like shape for engaging the engagement protrusions 41b of the intermediate foil piece 41a on both sides of the engagement protrusions 33a formed directly on the inner peripheral surface of the bearing housing 12 is provided. What is necessary is just to form an engagement recessed part, respectively.

Moreover, in the said embodiment, although the engaging groove 20 which engages the convex parts 21a and 21b of the top foil 9 was formed by fitting the fixing tool 16 in the through groove 13, such convex parts 21a and 21b are formed. Instead of the through groove 13, an engagement groove for engaging the shaft may be formed directly on the bearing housing 12.
Moreover, in the said embodiment, although the bearing housing was formed in the cylindrical shape, an annular flange may be integrally formed in one side surface or both side surfaces, and the whole may be formed in a substantially cylindrical shape. By forming the flange, it is possible to facilitate attachment to a turbomachine housing or the like.

DESCRIPTION OF SYMBOLS 1 ... Rotary shaft, 3 ... Radial foil bearing, 9 ... Top foil, 10 ... Intermediate foil, 10a ... Intermediate foil piece, 10b ... Engagement protrusion, 11 ... Back foil (bump foil), 11a ... Back foil piece, 11d DESCRIPTION OF SYMBOLS Engagement notch, 12 ... Bearing housing, 13 ... Through groove, 14 ... Locking groove, 15 ... Locking recess, 16 ... Fixing tool, 17 ... Base, 18 ... Bending piece, 19 ... Partition piece, 20 ... Engagement Alignment groove, 30 ... locking member, 31 ... first engagement recess (engagement recess), 32 ... groove, 33 ... engagement arm, 33a ... engagement projection, 34 ... coupling portion, 35 ... second engagement Recess (engagement recess), 40 ... radial foil bearing, 41 ... intermediate foil, 41a ... intermediate foil piece, 41b ... engagement protrusion, 42 ... bearing housing, 50 ... radial foil bearing, 51 ... bearing housing

Claims (7)

A radial foil bearing that is extrapolated to a rotating shaft and supports the rotating shaft,
A cylindrical top foil disposed to face the rotating shaft, an intermediate foil disposed radially outward of the top foil, a back foil disposed radially outward of the intermediate foil, and the top foil A cylindrical bearing housing that accommodates the intermediate foil and the back foil in an inserted state,
Engaging recesses extending from the inner peripheral edge to the outer peripheral edge of the bearing housing are formed opposite to each other on both side surfaces of the bearing housing, and the pair of engaging recesses are arranged in the circumferential direction of the bearing housing. Is formed in multiple,
The intermediate foil is configured to have a plurality of intermediate foil pieces arranged along the circumferential direction of the bearing housing,
The radial foil bearing according to claim 1, wherein the intermediate foil piece is formed with an engagement protrusion that engages with the engagement recess. The back foil is configured to have a plurality of back foil pieces arranged along a circumferential direction of the bearing housing.
The radial foil bearing according to claim 1, wherein the engaging protrusion of the intermediate foil piece is engaged with the engaging recess through a gap formed between the plurality of back foil pieces. On the inner peripheral surface of the bearing housing, an engagement groove having a shallow depth from the engagement recess toward the outer peripheral edge of the bearing housing is formed between the opposing engagement recesses.
The engagement recess and the engagement groove include a pair of engagement arms that engage with the engagement recess, a connection portion that engages with the engagement groove and connects the pair of engagement arms, And a locking member in which the opposite side of the pair of engaging arms to the side engaging with the engaging recess is an engaging projection protruding from the inner peripheral surface of the bearing housing. Stop,
Engagement notches that engage with the engagement protrusions are formed on both peripheral edges of the back foil,
The radial foil bearing according to claim 1, wherein the engagement protrusion of the intermediate foil piece engages with the engagement recess through the engagement notch of the back foil. Engagement notches communicating with the engagement recesses are formed on the peripheral edges on both sides of the back foil,
The radial foil bearing according to claim 1, wherein the engagement protrusion of the intermediate foil piece engages with the engagement recess through an engagement notch of the back foil. The back foil is configured to have a plurality of back foil pieces arranged along a circumferential direction of the bearing housing.
The radial foil bearing according to claim 3, wherein the engagement notch is formed in each of the back foil pieces.   The radial foil bearing according to claim 5, wherein the engagement notch of the back foil piece is formed at a central portion in the circumferential direction of the back foil piece.   The radial foil bearing according to any one of claims 1 to 6, wherein a plurality of the intermediate foils are stacked.

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